There are two time frames to consider here and I'm not sure which you are referring to. The first is the time to complete expansion. This is the time from the placement of the expanders to completed fill. This depends on the size of the breasts before surgery and your desired size afterwards. It can be shortened by choosing smaller implants. It is also impacted by issues in mastectomy healing and other factors such as chemotherapy/radiation therapy. The second timeframe is the time from completed expansion to implant exchange. Assuming all heals well and you expand completely, this is dependent on surgeon preference. Most surgeons will wait to allow for the capsule to form and soften( the scar around the expander), the swelling to go down, and the final pathology to be reviewed to assess whether chemotherapy and/or radiation therapy will be necessary. This can vary from surgeon to surgeon.